1. Technical Field
This disclosure generally relates to antenna assemblies and more particularly to antenna assemblies having both near-field and far-field characteristics.
2. Description of the Related Art
Wireless communications data-provider devices such as radio frequency identification (RFID) devices operate at various frequencies. Frequencies for RFID devices may, for example, include low frequency (LF 125-134.2 kHz), high frequency (HF 13.56 MHz), and ultra-high frequency (UHF 860-960 MHz).
Low frequency and high frequency RFID systems (LF/HF i.e. 13.56 MHz) are short-range systems based on inductive coupling between respective antennas of a reader and a data-provider device through a magnetic field. Ultra-high frequency (UHF i.e. 860-960 MHz) and microwave (i.e. 2.4 GHz and 5.8 GHz) RFID systems can be long-range systems that use electromagnetic waves propagating between respective antennas of a reader and data-provider device.
UHF RFID systems designed to operate over long distances through electromagnetic wave propagation have several advantages including range compared to LF/HF systems but their performance in general is more susceptible to the presence of various dielectric and conducting objects in the vicinity of the data-provider device.
HF and some UHF RFID systems are designed to operate using magnetic induction and perform over a relatively a short distance. These systems are less susceptible to the presence of various dielectric and conducting objects in the vicinity of the data-provider device, however their limited range severely restricts their broad application.
The nature of electromagnetic wave propagation and magnetic inductance are substantially different and consequently so are their respective tag and reader antenna designs. Due to this physical limitation, there has never existed a system which exhibits the performance characteristics of both near and far field RFID devices.
Near-field RFID may provide a possible solution for item level tagging (ILT) in various industries such as pharmaceutical and retailing industry. Near-field coupling is already being used in such areas of UHF RFID as printer coupler ((tag writer) and for conveyor belt applications. Other near-field HF, UHF, and microwave applications, to name a few, include short range wireless communication, also known as near field communication (NFC), hyperthermia treatment, MRI imaging, detection of buried objects, measuring material properties and various modulated scattering probe techniques.
Far-field RFID is currently providing solutions to many logistics and tracking applications where upwards of hundreds of tags per second can be read over great distances.
There is a need for systems, methods, and devices that may wirelessly communicate both over relatively long distances such as with a far-field wireless communications device and over relatively short distances such as with a near-field wireless communications device so as to enjoy the performance advantages of both while dramatically reducing the cost and complexity of having two separate systems.